How much are silver dollar coins worth?

It depends on what year they are, what condition they are in, and whether they are circulated or not.

True silver dollars (made of 90% silver) were minted from 1794 to 1935 at 5 different mints so "whatzit worth?" is far to broad to answer specifically.

US "silver" dollars and half dollars minted after 1970 (along with quarters and dimes minted after 1964) are really copper coins with a copper-nickel or bronze outer cladding. Unless they are uncirculated, they are worth no more than face value as collector coins.

However, those minted in 1935 or earlier are worth considerably more than $1 at the current price of silver, and possibly much more as collectibles so you should check their values in a standard coin guide. In any case you'll get the lowest prices from one of those "we buy gold" places so you need to do more research before selling them.